In recent years, a variety of techniques have been proposed for improving safety in vehicle driving. As one such method, there has been proposed a moving object recognizing apparatus for recognizing, as a moving object, a vehicle approaching a self vehicle, recognizing in particular, another vehicle approaching from behind the self vehicle as a moving object. As shown below, Patent Documents 1-3 show the techniques relating to such moving object recognition.
Patent Document 1 (JP6-130076A) discloses a method for detecting a vehicle traveling obliquely reward of a self vehicle. In this method, the vehicle traveling obliquely rearward is detected based upon an optical flow derived from captured images and a further optical flow corresponding to a traveling velocity of the self vehicle obtained by a vehicle speed sensor. More particularly, the method detects the vehicle, based upon agreement/disagreement between the optical flow obtained by image processing and the further optical flow calculated as motion vector of a time series of images captured at the traveling velocity of the self vehicle. And, in the event of detection of such vehicle traveling obliquely rearward, an image processing/calculating section outputs a drive signal to an alarming section, which in turns issues an alarm.
Patent Document 2 (JP9-86314A) discloses a vehicle rear-side monitoring apparatus capable of effectively recognizing another vehicle even during dark-place traveling such as night traveling or traveling in a tunnel. According to this vehicle rear-side monitoring apparatus, a traveling direction detecting means and a traveling distance detecting means cooperate to detect an amount of movement of the self vehicle, based on which the position of infinite distance for optical flow calculation is varied. That is to say, with this apparatus, by rendering the infinite distance position variable not relying on the image data, sufficient recognition precision is ensured even at the time of dark place traveling. Then, the apparatus alarms the driver through its alarming section, depending on a degree of necessity of alarming calculated based on the calculated optical flow.
Patent Document 3 (JP6-282655A) discloses a technique which allows effective recognition of a moving object present around a self vehicle, based upon an obtained optical flow even when the self vehicle is not traveling straight. In this technique, there is provided a motion direction detecting means for detecting motion direction data of self vehicle, and a group of classified optical flows are corrected based upon this motion direction data. Namely, in this technique, a moving object is detected, with compensation of an influence exerted to the optical flows by the movement of the self vehicle. Then, a relative velocity is calculated from the position of the self vehicle relative to the traveling path and the optical flows. And, if it is determined based on a distance signal from a distance sensor that alarming is needed, an alarming device is activated.                Patent Document 1: JP6-130076A (paragraphs 8-16, FIGS. 3, 4, etc.)        Patent Document 2: JP9-86314A (paragraphs 9, 16-19, 64-66, etc.)        Patent Document 3: JP6-282655A (paragraphs 6-12, etc.)        